[Objective] The aim of this study was to evaluate the effect of livestock exclusion on the health of grassland ecosystem accurately and quantitatively. [Method] One open grazing site and five seasonal exclusion sites,...[Objective] The aim of this study was to evaluate the effect of livestock exclusion on the health of grassland ecosystem accurately and quantitatively. [Method] One open grazing site and five seasonal exclusion sites, which had the same vegetation composition （taking Leymus chinensis and Stipa krylovii as main species） and soil type, were chosen as research objects for the VOR and CVOR evaluation of the effect of open grazing and livestock exclusion on the health of typical steppes, and for building the calculation model for VOR and CVOR indices to evaluate the health of typical steppes with different exclusion periods. [ Result] The VOR and CVOR composite indices both could accurately evaluate the health of typical steppes, and the evaluation results from the both indices were quite consistent. Although the condition （C）, vigor（V）, organization （O） and resilience（ R ） indices changed differently in different exclusion periods, the VOR and CVOR composite indices increased gradually with the peri- od of exclusion prolonged, and the health condition of typical steppe changed from ＂alert＂ level （in the open grazing and earlier exclusion period） to ＂healthy＂ level （after 13 to 20 years＇exclusion）. [ Conclusion] The application of exclusion was beneficial to the recovery of degraded grassland ecosystem.展开更多
为解决传统聚类算法无法兼顾时间序列数量和形状特征、聚类数确定依据不足等问题,提出了一种基于量-形距离的同步回代缩减算法(simultaneous backward reduction algorithm based on quantity-contour distance,SBRQC)。首先,将反映风...为解决传统聚类算法无法兼顾时间序列数量和形状特征、聚类数确定依据不足等问题,提出了一种基于量-形距离的同步回代缩减算法(simultaneous backward reduction algorithm based on quantity-contour distance,SBRQC)。首先,将反映风电出力过程线数量、形状、峰谷差等特性指标引入同步回代缩减(simultaneous backward reduction,SBR)算法,对风电出力过程场景进行缩减,得到不同场景数下的风电出力过程及对应概率。其次,综合考虑类内相似度和类间差异度,提出新的聚类有效性指标场景缩减(scenario reduction,SD)作为确定提取场景数的依据。最后,以人工数据集和某区域电网风电日出力过程为例,验证了SBR-QC算法的合理性和准确性。展开更多
基金supported by National Key Fundamental Research and Development Fund of China (No.2007CB106800)
文摘[Objective] The aim of this study was to evaluate the effect of livestock exclusion on the health of grassland ecosystem accurately and quantitatively. [Method] One open grazing site and five seasonal exclusion sites, which had the same vegetation composition （taking Leymus chinensis and Stipa krylovii as main species） and soil type, were chosen as research objects for the VOR and CVOR evaluation of the effect of open grazing and livestock exclusion on the health of typical steppes, and for building the calculation model for VOR and CVOR indices to evaluate the health of typical steppes with different exclusion periods. [ Result] The VOR and CVOR composite indices both could accurately evaluate the health of typical steppes, and the evaluation results from the both indices were quite consistent. Although the condition （C）, vigor（V）, organization （O） and resilience（ R ） indices changed differently in different exclusion periods, the VOR and CVOR composite indices increased gradually with the peri- od of exclusion prolonged, and the health condition of typical steppe changed from ＂alert＂ level （in the open grazing and earlier exclusion period） to ＂healthy＂ level （after 13 to 20 years＇exclusion）. [ Conclusion] The application of exclusion was beneficial to the recovery of degraded grassland ecosystem.
